Machine tool for cutting plate and sandwich panels

ABSTRACT

A machine for cutting plate-shaped workpieces, incorporates a tool guide ( 7 ), an operating handle ( 13 ), and a cutting tool ( 6 ) which revolves along the tool guide ( 7 ). By moving the operating handle ( 13 ), the tool guide ( 7 ) with its cutting tool ( 6 ) can be shifted from an idle position into an active position. In its idle position the cutting tool ( 6 ) is disengaged from, and, in its active position it is engaged in, the workpiece to be processed. Provided between the operating handle ( 13 ) and the tool guide ( 7 ) is a gearing mechanism ( 14, 18 ) with a transmission ratio which varies with the movement of the operating handle ( 13 ) as a function of the position of the tool guide ( 7 ) and its cutting tool ( 6 ) relative to the workpiece.

[0001] This invention relates to a machine for cutting plate-shaped workpieces and especially sandwiched plates, incorporating a tool guide with a revolving power-driven cutting tool as well as a manual operating handle by means of which the tool guide with the cutting tool can be moved from an idle position into an active position, whereby in its idle position the cutting tool is disengaged from the workpiece and in its active position it engages in the workpiece to be cut.

[0002] A machine of this type has been described in DE-U-298 15 228. The prior-art device is a hand-operated machine tool in which a machine base unit is provided with a guide rail along which a cutting chain revolves in continuous fashion. The machine base unit is mounted in horizontally pivotable fashion on a base plate that bears down on the object workpiece. For starting a cut in the workpiece the machine base unit with the guide rail and the revolving cutting chain is tilted around its pivoting axis on the base plate. From an idle position away from the workpiece the guide rail with the cutting chain is lowered into the workpiece. This prior-art machine is used for cutting sandwiched plates, meaning multilayer workpieces whose individual layers differ from one another in terms of mechanical strength. Such multilayer plates typically consist of a foam core sandwiched between cover layers in the form of thin metal sheets most commonly made of steel.

[0003] It is the objective of this present invention to introduce a machine that offers an optimum in manipulability.

[0004] According to the invention this objective is achieved with the combined features specified in claim 1. These include a gearing mechanism between the manual operating handle and the tool guide that allows the machine operator to optimally balance the amount of pressure applied on the operating handle relative to the force effectively applied in the cutting process between the tool guide and cutting tool and the workpiece. This capability is of particularly practical significance in view of the fact that moving the tool guide with the cutting tool from its idle position into its active position meets with a counteracting force i.e. resistance from the workpiece that varies with the progressive phases of the tool movement. Essentially at the start of the cut, the tool guide with the cutting tool must address the workpiece with substantially more pressure than is necessary toward the end of the cutting process. The gearing mechanism according to the invention generally or at least largely relieves the machine operator of the need to make adjustments to the amount of pressure applied by him and transmitted via the operating handle. The gearing mechanism in the machine according to the invention supports and adaptively manages the force needed by the tool guide and cutting tool for the various phases of the cutting process. Quite significantly, this also helps to avoid too much pressure by the cutting tool on the workpiece with resultant excessive wear or even damage to the cutting tool.

[0005] Specific design variations of the invention described in claim 1 are covered in the subclaims 2 to 10.

[0006] In the case of the configuration per this invention described in claim 2, machine operation is optimized in that the pressure that needs to be applied by the operator on the operating handle is essentially uniform throughout the entire cutting process.

[0007] Substantial design flexibility as well as functional ruggedness are offered by a lever-type gearing mechanism provided between the operating handle and the tool guide in the design version of this invention described in claim 3.

[0008] A gearing mechanism that requires only a minimum of components, thus permitting for instance a small and light-weight design, is obtainable by locating the operating handle directly next to the pivot arm on the operator side and/or by designing the tool guide itself as a pivot arm on the workpiece side (claim 4).

[0009] The characterizing features of claims 5 and 6 serve the primary purpose of making it possible for the operator to monitor the machining of the workpiece.

[0010] The scales specified in these claims enable the operator to locate the point of attack on the object workpiece even though that point of attack is not within his field of view and in spite of the fact that, due to the variable transmission ratio, identical path lengths in the movement of the operating handle result in different respective path lengths in the movement of the tool guide and cutting tool.

[0011] The feature provided in the design version of this invention according to claim 7 allows the operator to let go of the operating handle at any time during the cutting process without in any way compromising operational safety or affecting the functional reliability in the progression of the work. Claims 8 and 9 describe technically advantageous structural approaches to the implementation of the basic concept per claim 7.

[0012] Machines designed according to this invention as described in claim 10 offer the advantage of easily permitting operation by right-handed as well as left-handed persons.

[0013] The following will explain the invention in more detail with the aid of schematic illustrations of a design example, in which—

[0014]FIGS. 1 and 2 are isometric views of a machine for cutting sandwiched plates;

[0015]FIG. 3 is a top view of the machine per FIGS. 1 and 2 in the direction of the arrow III in FIG. 1;

[0016] FIGS. 4 to 6 depict the machine per FIGS. 1 to 3 in different phases of cutting into a sandwiched plate; and

[0017]FIG. 7 shows the operator-side swivel arm of the machine per FIGS. 1 to 6 with an associated locking device.

[0018] As can be seen in FIGS. 1 and 2, a machine for cutting sandwiched plates 2 includes a base plate 3 supporting a machine housing 4 and, flange-mounted on the machine housing 4, an electric drive motor 5. The latter is functionally connected via a shiftable clutch to a drive wheel of a sawchain 6 that constitutes the cutting tool.

[0019] The sawchain 6 revolves around a tool guide in the form of a paddle blade 7. The direction of travel of the sawchain 6 on the paddle blade 7 is indicated by an arrow 8. The blade 7 with its revolving sawchain 6, swivel-mounted on the machine housing 4, can swivel on a pivot 9 in the direction of the double arrow 10. A protective enclosure 11 with a vacuum-cleaner port 12 covers the area of the swivel mount of the blade 7 on the machine housing 4. The pivot 9 of the blade 7 coincides with the axis of the drive wheel of the sawchain 6.

[0020] A handle 13 serves to tilt the blade 7 and is mounted at the free end of the swivel arm 14 on the operator side. The swivel arm 14 on its part is swivel-mounted, tiltable around a pivot 15 in the direction of a double arrow 16, on a bearing block 17 that is connected to the base plate 3. A transmission lever 18, only marginally visible in FIGS. 1 and 2, is rotatably attached at one end to the swivel arm 14 on the operator side and with its other end to the paddle blade 7. The linkage points of the transmission lever 18 are spaced at a distance from both the pivot 15 of the operator-side swivel arm 14 and the pivot 9 of the blade 7.

[0021] Integrated into the operating handle 13 is a pressure switch 19. A pressure switch 20 and a pushbutton 21 are installed on a support handle 22 that is mounted on the base plate 3 of the machine 1. An enclosure serving as the paddle-blade cover 23 extends from the support handle 22 in the direction of the opposite end of the base plate 3.

[0022] The edges of the base plate 3 are provided with a number of reference or marker notches. Specifically, these include a marker notch 24 on the blade-side transverse edge of the base plate 3 and marker notches 25, 26, 27, 28 on one longitudinal edge and marker notches 29, 30, 31, 32 on the other longitudinal edge of the base plate. The vertex of the marker notch 24 extends in the longitudinal center plane through the narrow sides of the paddle blade 7. It is aligned with a V-shaped longitudinal groove 33 on the cover 11 of the blade 7 and sawchain 6. Also coinciding with the aforementioned longitudinal center plane of the blade 7 is the common center plane of the operating handle 13 and the support handle 22.

[0023] On the longitudinal edge of the base plate 3, facing the viewer in FIG. 1, a dual scale 34 is mounted next to the marker notches 25, 26, 27, 28. As can be seen in FIG. 3, the dual scale 34 features lettered graduation marks 35. These markings 35 match the graduations 36 of a dual scale 37 provided on the bearing block 17 of the operator-side swivel arm 14. As can also be seen in FIG. 3, the operator-side swivel arm 14 is provided with a pointer 38 and, opposite the latter, a pointer 39.

[0024] Also shown in FIG. 3 is a Bowden cable 40 extending from the operating handle 13, as well as a Bowden cable 41 extending from the support handle 22. An On/Off switch 42 is located on the top side of the electric drive motor 5.

[0025] FIGS. 4 to 6 illustrate the functional progression of the machine 1 in practical use.

[0026] In FIG. 4, the paddle blade 7 with the sawchain 6 is in its idle position. The end of the blade 7, protruding beyond the protective cover 11, is fully tilted into the inside of the blade cover 23. The electric drive motor 5 is switched off, the sawchain 6 stands still. With its base plate 3 the machine 1 rests on the sandwiched plate 2 that is to be processed. The machine 1 was previously carried to the work area with the operating handle 13 and the operator-side swivel arm 14 in the position shown. In that particular position the machine 1 is well balanced at the operating handle 13. In other words, even in terms of transportation the machine 1 is user-friendly.

[0027] As the first step for using the machine 1 the operator moves the On/Off switch 42 on the electric drive motor 5 in the On position. When the drive motor 5 is running, the operator grasps the support handle 22 with one hand, the operating handle 13 with the other hand.

[0028] Depressing the pushbutton 21 and then the pressure switch 20 engages the clutch between the drive motor 5 and the drive wheel of the sawchain 6 via the Bowden cable 41, setting the sawchain in motion. The positive drive connection between the drive motor 5 and the drive wheel of the sawchain 6 is maintained for as long as the pressure switch 20 remains depressed. The free end of the blade 7 with the sawchain 6 is at the level of the marker notches 27, 31 or at the level of the marker notches 28, 32, depending on whether the short or the long version of the paddle blade 7, available in two lengths, is being used.

[0029] After the electric drive motor 5 and with it the sawchain 6 has reached its full rotational speed, the operator depresses the pressure switch 19 on the operating handle 13 and he can now move the handle 13 by turning the operator-side swivel arm 14 per FIG. 4 in the clockwise direction. Depressing the pressure switch 19 releases a locking device 43, illustrated in FIG. 7 and described in detail further below.

[0030] The operator-side swivel arm 14 is tilted around its pivot 15. That causes the transmission lever 18 to shift, which in turn tilts the paddle blade 7, constituting a swivel element on the side of the workpiece, around its pivot 9. In the process the blade 7 with its revolving sawchain 6 turns counterclockwise from its idle position per FIG. 4. The blade 7 with its revolving sawchain 6 exits from the blade cover 23 and the sawchain 6 cuts from the top into the sandwiched plate 2.

[0031] In this phase of the cutting process the blade 7, i.e. the sawchain 6, must exert relatively strong pressure on the sandwiched plate 2. Only such relatively strong pressure can overcome the large-surface resistance offered by the outer layer of the sandwiched plate 2 as the blade 7 with the sawchain 6 starts to cut into it. That notwithstanding, the operator needs to apply only easily mustered initial strength on the operating handle 13, a fact ensured by the way the gearing mechanism including the operator-side swivel arm 14 and the transmission lever 18 for the blade 7 with sawchain 6 is configured. The fulcrums of the transmission lever 18 on the operator-side swivel arm 14 and on the blade 7 are located correspondingly.

[0032] The first, most pressure-intensive phase of cutting into a sandwiched plate 2 ends when the blade 7 with the sawchain 6 has reached a position relative to the sandwiched plate 2 that is shown in FIG. 5. At this point the blade 7 and sawchain 6 are in an attack position on the sandwiched plate 2 but have not engaged yet. For moving the blade 7 and sawchain 6 into their final cutting position the operating handle 13, with the pressure switch 19 held depressed, must be moved further from its position per FIG. 5 in the clockwise direction. The blade 7 and sawchain 6 are at the final point of attack when they have reached the position shown in FIG. 6. At that point the blade 7 with its sawchain 6 extends downward, perpendicular to the sandwiched plate 2.

[0033] The movement of the blade 7 and sawchain 6 from their position per FIG. 5 into the position per FIG. 6 meets with relatively little resistance. A correspondingly minor amount of pressure needs to be applied on the blade 7 and the sawchain 6 in the direction of the sandwiched plate 2. This, too, is reflected in the configurational design of the gearing mechanism consisting of the operator-side swivel arm 14 and the transmission lever 18, i.e. specifically by virtue of the location of the fulcra of the transmission lever 18 on the operator-side swivel arm 14 and on the paddle blade 7.

[0034] A comparison of the pivoting angles by which the operator-side swivel arm 14 has been moved from its position per FIG. 4 to its position per FIG. 5 and again from its position per FIG. 5 into the position per FIG. 6, with the correspondingly related pivoting angle of the blade 7 will make it evident that the pivoting angles of the operator-side swivel arm 14 and of the blade 7 are essentially identical for the movement from the position per FIG. 4 into the position per FIG. 5, whereas, in the movement from the position per FIG. 5 into the position per FIG. 6, the pivoting angle of the blade 7 is significantly larger than the concomitant pivoting angle of the operator-side swivel arm 14. In the first phase of the cut into the sandwiched plate 2 the gearing mechanism between the operating handle 13 and the blade 7 works at a transmission ratio of 1:1 and in the second phase the “transmission” ratio is 1:0.6. Even though the amount of pressure that must be applied on the blade 7 with sawchain 6 in the direction of the sandwiched plate 2 changes between phases, the pressure that the operator needs to exert on the operating handle 13 remains essentially the same throughout the cutting process.

[0035] Throughout the overall processing of the sandwiched plate 2 and especially throughout the entire cutting process, the operator can tell at any time the position of the blade 7 and sawchain 6 relative to the sandwiched plate 2. This is made possible by the dual scale 37 on the bearing block 17 for the operator-side swivel arm 14 and the dual scale 34 on one longitudinal edge of the base plate 3. Which half of the indicator scales 34, 37 is used will again depend on whether the short or the long version of the blade 7 is employed. The short scale halves are used in conjunction with the short version of blade 7, the long scale halves are used in conjunction with the long blade 7.

[0036] As the operator-side swivel arm 14 is tilted, the pointers 38, 39 move along the dual scale 37. The inscription on the graduation lines 36 of the dual scale 37 indicates in millimeters the depth to which the blade 7 with the sawchain 6 extends below the base plate 3, i.e. the depth to which the sawchain 6 has cut into the sandwiched plate 2 that is being processed. The same-number graduation mark 35 on the dual scale 34 indicates the forward position of the leading edge of the tilted sawchain 6. Accordingly, the scale 34 shows how far the cut has progressed.

[0037] When the blade 7 with its sawchain 6 is in its final active position (FIG. 6), the leading edge of the sawchain 6 will be at the level of marker notches 25, 29, the trailing edge of the sawchain 6 will be at the level of marker notches 26, 30 on the longitudinal outer edge of the base plate 3.

[0038] From its status per FIG. 6, the machine 1 can be advanced in the forward direction 44 relative to the sandwiched plate 2 until the cut has reached the desired length. Particularly useful in this forward movement is the fact that the common central plane of the operating handle 13 and support handle 22 coincides with the center plane of the paddle blade 7. It follows that the point at which the operator begins to apply pressure and the point at which the sawchain 6 engages the sandwiched plate 2 are located in exactly the same plane. This facilitates the straight-line advance of the machine in the forward direction 44, further aided by the longitudinal groove 33 that extends in the forward direction on the protective enclosure 11 and, its apex aligned with that groove, by the marker notch 24.

[0039] When the operator releases the pressure switch 19 while the sawchain 6 is revolving, it forces activation of the Bowden cable 40. This Bowden cable is part of the locking device 43, illustrated in detail in FIG. 7.

[0040] As shown in that illustration, the forward section 46 of the flexible tube 45 of the Bowden cable 40 is held in place by a forward clamping lever 47, its rearward section 48 is held by a rearward clamping lever 49. A wire 56 extends through the interior of the flexible tube 45. A preloaded compression spring 50 pushes the forward clamping lever 47 against a stop 51 and the rearward clamping lever 49 against a stop 52. Extending through the forward clamping lever 47 and the rearward clamping lever 49 is a lock rod 53 that is supported in longitudinally movable fashion on the bearing block 17 of the operator-side swivel arm 14. By way of a gate link 54 the lock rod 53 connects with its forward end to an extension 55, beyond the pivot 15, of the operator-side swivel arm 14.

[0041] In the operating state per FIG. 7 the lock rod 53 is clamped in a locked position in the longitudinal direction inside its passages through the forward clamping lever 47 and the rearward clamping lever 49. Accordingly, the operator-side swivel arm 14 is locked and prevented from rotating around its pivot 15 in either one of the two possible tilting directions. Consequently, the paddle blade 7, coupled to the swivel arm 14 via the transmission lever 18, is likewise prevented from changing its tilted position.

[0042] Now, if in the situation per FIG. 7 the operator depresses the pressure switch 19 on the operating handle 13, the forward section 46 and the rearward section 48 of the flexible tube 45 will shift relative to the wire 56 of the Bowden cable 40. As a result, the forward clamping lever 47 and the rearward clamping lever 49 will move with their lower ends, per FIG. 7, toward each other against the action of the compression spring 50. This causes the forward clamping lever 47 and the rearward clamping lever 49 to assume an angled position relative to the lock rod 53, unjamming the lock rod 53 in the oversized passages surrounding it in the forward clamping lever 47 and the rearward clamping lever 49. The lock rod 53 is now free to move in the longitudinal direction. Thus releasing the lock rod 53 unlocks the operator-side swivel arm 14 with the operating handle 13. The blade 7 with the sawchain 6 is equally free to swivel.

[0043] If at this juncture the pressure switch 19 is released, the preloaded compression spring 50 will automatically restore the operating state per FIG. 7 and will thus automatically lock the blade 7 with its revolving sawchain 6 in position. 

Having thus described the invention, what is claimed is:
 1. Machine for cutting plate-shaped workpieces comprising: (a) a housing (4); (b) a tool guide (7) pivotally mounted on the housing (4); (c) a motor-driven cutting tool (6) extending about the tool guide (7); (d) a grippable operating handle (13) pivotably supported in the housing (4) and operatively connected to the tool guide (7) to shift the tool guide (7) with the cutting tool (6) from an idle position into an active position, whereby in its idle position the cutting tool (6) is disengaged from, and in its active position it is engaged in, the workpiece (2) to be cut; and (e) a gearing mechanism (14, 18) provided between the operating handles (13) and tool guide 7, said gearing mechanism having a transmission ratio that varies with the movement of the operating handle (13) as a function of the position of the tool guide (7) and cutting tool (6) relative to the workpiece (2).
 2. The cutting machine in accordance with claim 1, wherein the variation of the transmission ratio is so dimensioned that the amount of pressure that must be applied by the operator to move the operating handle (13) from the idle position of the tool guide (7) with its cutting tool (6) into and throughout the cutting process is substantially uniform.
 3. The cutting machine in accordance with claim 2 wherein the gearing mechanism (14, 18) between the operating handle (13) and the tool guide (7) is a lever transmission.
 4. The cutting machine in accordance with claim 1 wherein the operating handle (13) is mounted on an operator-side pivot arm (14) and can be pivoted together with the operator-side pivot arm (14) around the pivotal axis (15) of the pivot arm (14).
 5. The cutting machine in accordance with claim 1 wherein the tool guide (7) provides the pivot arm on the side of the workpiece.
 6. The cutting machine in accordance with claim 1 wherein there is included at least one scale (37) indicating the respectively current maximum cutting depth of the cutting tool (6) in the workpiece as a function of at least one respectively current position of the operating handle (13) during its movement.
 7. The cutting machine in accordance with claim 1 wherein there is included at least one scale (34) indicating the position of the tool guide (7) with its cutting tool (6) relative to the workpiece at the current maximum cutting depth of the cutting tool (6).
 8. The cutting machine in accordance with claim 1 wherein there is included a locking device (43) for automatically locking the tool guide (7) with its cutting tool (6) in a position assumed during its movement.
 9. The cutting machine in accordance with claim 8 wherein the locking device (43) for the tool guide (7) with its cutting tool (6) is provided with a clamping mechanism that can be released against the action of an elastic restoring force.
 10. The cutting machine in accordance with claim 1 wherein the operating handle (13) is mounted on an operator-side pivot arm (14), wherein the tool guide (7) is connected to the operator-side pivot arm (14) by a transmission lever (18), and wherein there is included a locking device designed to engage in the operator-side pivot arm (14) so that the tool guide (7) may be automatically locked in any of its respectively current positions during its movement.
 11. The cutting machine in accordance with claim 1 wherein there is included a support handle (22) and wherein the operating handle (13) and the support handle (22) are positioned along a line that extends parallel to the feed direction (44), whereby, with the tool guide (7) and its cutting tool (6) in their active position, the machine (1) and the workpiece to be processed can be moved relative to each other in the feed direction (44). 